The invention relates to splash or mist lubricated sleeve bearings, and more particularly to such a bearing that is especially adapted for use on a connecting rod big end which is journalled on a throw or pin of a crankshaft.
Lubrication of connecting rod big end bearings has long been known through the aid of splash or oil mist, but with this method there is no way of guaranteeing that a controlled or satisfactorily adjustable amount of lubricant will be supplied. Further, because there is not a well defined flow of lubricant through the bearing, cooling of the bearing surfaces is primarily obtained by conduction of heat through the connecting rod and the crankshaft rather than by supplying relatively cool lubricant to, and removing heated lubricant from, the bearing.
To guarantee a supply and flow of oil to and through the bearing, it is also well known to use pressure lubrication, but this requires an oil pump which is an additional part, as well as a mechanical drive for the oil pump. Further, because a crankshaft throw is continually moving with respect to the frame of the rest of the machine, the entire machine and crankshaft are made larger and more complex because of the need for associated ducts and passageways through the crankshaft. This tends to make the construction of pressure lubricated machines relatively expensive.
The use of spiral grooves to provide lubrication of a plain bearing has also been proposed. British patent specification 21,833 shows helical grooves in a cylindrical surface for carrying oil upward from a sump and supplying it to a plain cylindrical shaft bearing. British Pat. No. 239,138 similarly shows a helical groove which conducts oil from a cavity to a thrust bearing. However, each of these bearing arrangements requires a substantial screw element to move the lubricant, thus substantially lengthening the bearing arrangement.
In another proposed arrangement according to U.S. Pat. No. 3,494,674, both axial and radial loads can be supported by a bearing having a helical groove for pressurizing lubricant in a shaft end journal, and a spiral groove in the end surface of the shaft for pumping lubricant toward the center of the thrust bearing to develop a high thrust force. However, no significant flow through the bearing will occur, so that removal of heat by the lubricant is not possible.